Answers

I have an old SAL rulebook, circa 1962, and can answer most specific
questions about CTC signal aspects. The SCL rulebook mentioned is
probably good on the SAL lines as well, as the signals continue to be
used on active lines to this day.

While I don't have an answer for you on the SAL signal question, I'm
sure it can be found in an SAL rule book. I have an SCL book from
1972 and it's signal rules are almost exactly the same as those in
the 1997 CSX book (The former SCL section, not the Chessie).
If you get hold of an old Seaboard book, let us know!